A method of recycling plastic waste comprising pet

Abstract

A method of recycling a plastic product comprising PET is provided. The method comprises combining a plastic product comprising PET, a heterogeneous metal oxide catalyst and a solvent to provide a reaction mixture and heating the mixture by microwave irradiation to provide reaction product.

1 . A method for recycling a plastic product comprising PET, the method comprising,
 combining a plastic product comprising PET, a catalyst comprising calcium oxide (CaO), zinc oxide (ZnO), magnesium oxide (MgO), iron oxide (Fe 2 O 3 ), or a catalyst derived from CaO, and a solvent to provide a reaction mixture,   heating the reaction mixture by microwave heating to provide a reaction product comprising a depolymerisation product.   
     
     
         2 . The method of  claim 1 , wherein the catalyst is heterogenous. 
     
     
         3 . The method of  claim 1 or 2 , wherein the catalyst is nanostructured. 
     
     
         4 . The method of  any one of the preceding claims , wherein the catalyst is CaO. 
     
     
         5 . The method of  any one of the preceding claims , wherein the catalyst comprises CaO mixed with any one of zinc oxide (ZnO), magnesium oxide (MgO), iron oxide (Fe 2 O 3 ). 
     
     
         6 . The method of any one of  claims 1 to 3 , wherein the catalyst is one derived from CaO and is one prepared from combining CaO and a triol. 
     
     
         7 . The method of  claim 6 , wherein the triol is selected from the group comprising glycerol, pentane-1,3,4-triol, propane-1,2,3 triol, cyclohexane-1,2,3-triol, butane-1,2,4-triol, Butane-1,1,3-triol, pentane-1,3,4-triol, cyclohexane-1,2,3-triol, propane-1,2,3-triol and glycerin. 
     
     
         8 . The method of  claim 6 or 7 , wherein the catalyst is calcium glyceroxide. 
     
     
         9 . The method of  any one of the preceding claims , wherein the catalyst is a supported catalyst. 
     
     
         10 . The method of  claim 9 , wherein the supported catalyst is selected from the group comprising CaO/MgO, activated carbon supported CaO, nano CaO, CaO on AC (activated carbon and activated charcoal) supports and ZnO/CaO mixture. 
     
     
         11 . The method of  any one of the preceding claims  wherein the solvent is selected from ethylene glycol and 1, 4-butanediol. 
     
     
         12 . The method of  any one of the preceding claims , further comprising a step of recovering the depolymerisation product from the reaction product. 
     
     
         13 . The method of  claim 12 , wherein the step of recovering the depolymerisation product is by crystallisation. 
     
     
         14 . The method of  any one of the preceding claims , further comprising a step of solvent recovery and/or a step of catalyst recovery. 
     
     
         15 . The method of  claim 14 , wherein the step of solvent recovery or catalyst recovery is by filtration. 
     
     
         16 . The method of  any one of the preceding claims , wherein the catalyst is dispersed in the solvent prior to additional of the plastic product. 
     
     
         17 . The method of  claim 16 , wherein the catalyst and solvent are stirred and/or agitated prior to addition of the plastic product. 
     
     
         18 . The method of  any one of the preceding claims , wherein the solvent is ethylene glycol, and the reaction product comprises bis-hydroxy ethylene terephthalate (BHET). 
     
     
         19 . The method of any one of  claims 1 to 17 , wherein the solvent is 1, 4-butanediol, and the reaction product comprises bis-hydroxy butylene terephthalate (BHBT). 
     
     
         20 . The method of  any one of the preceding claims , wherein the catalyst is included in the reaction mixture at a concentration of 0.1% to 2% by weight of PET. 
     
     
         21 . The method of  any one of the preceding claims , wherein the plastic product and the solvent are present in a ratio of 20:1. 
     
     
         22 . The method of  any one of the preceding claims , wherein the reaction mixture comprises a microwave absorber. 
     
     
         23 . The method of  claim 22 , wherein the microwave absorber may be selected form the group comprising sodium chloride, sodium bromide, sodium iodide, sodium fluoride, lithium chloride, potassium chloride, magnesium chloride, calcium chloride and activated charcoal. 
     
     
         24 . The method of  any one of the preceding claims , wherein the plastic product comprises PET and cotton, the method further comprises an initial treatment step to separate the PET and cotton. 
     
     
         25 . The method of  claim 24 , wherein the initial treatment step comprises placing the product in a suspension of glycerol, or ethylene carbonate, and subjecting it to microwave irradiation. 
     
     
         26 . The method of  claim 25 , wherein the separated cotton is removed from the suspension by filtration and the PET is dried. 
     
     
         27 . The method of  any one of the preceding claims , further comprising a step of polymerisation of the depolymerisation product. 
     
     
         28 . A depolymerisation product produced by the method of any one of  claims 1 to 26 . 
     
     
         29 . A method of converting PET into bis-hydroxy ethylene terephthalate (BHET), the method comprising
 combining PET or a PET containing product, a catalyst comprising calcium oxide (CaO), zinc oxide (ZnO), magnesium oxide (MgO), iron oxide (Fe 2 O 3 ), or calcium glyceroxide and ethylene glycol to provide a reaction mixture,   heating the reaction mixture by microwave heating to produce BHET.   
     
     
         30 . A method of converting PET into bis-hydroxy butylene terephthalate (BHBT), the method comprising
 combining a PET or a PET containing product, a catalyst comprising calcium oxide (CaO), zinc oxide (ZnO), magnesium oxide (MgO), iron oxide (Fe 2 O 3 ), or calcium glyceroxide and butylene diol,   heating the reaction mixture by microwave heating to provide BHBT.